The magneto-plasmon dispersion relation of a quasi-three-dimensional electron gas confined in a wide AlxGa1-x As parabolic quantum well is investigated in the magnetic quantum limit. Magneto-plasma excitations polarized perpendicular to the magnetic field and with wave vector q of the order of the inverse magnetic length 1 l0 are measured in far infrared magneto-transmission experiments on 100 nm thick electron slabs. A minimum is found in the magneto-plasma mode frequency at ql0 ≈ 2 suggesting the existence of a magneto-roton excitation. The collective excitation spectrum is calculated in analogy with Feynman's theory for rotons in helium, and is found to be in good qualitative agreement with the measurement.
All Science Journal Classification (ASJC) codes
- Condensed Matter Physics
- Surfaces and Interfaces
- Surfaces, Coatings and Films
- Materials Chemistry